1. Field of the Invention
This invention relates to calibration techniques, and more particularly to systems and methods for phase response self-calibration of instrumentation.
2. Description of the Related Art
Signal components are delayed when passing through a device such as communications receiver or similar instrumentation. The signal delay is often different for different frequencies. The delay variation means that signals consisting of different frequency components suffer delay (or time) distortion. Group delay is a measure of time distortion, and is typically calculated by differentiating the insertion phase response of the device under test (DUT) versus frequency.
In some instances calibration techniques are employed to account for delay, thereby helping to improve phase linearity of a device. With regard to communications receivers, phase linearity, as well as flat magnitude response, across an analysis bandwidth (BW) may be critical to prevent or minimize distortion of received signals. With regard to modular devices/instrumentation, such as those including a plurality of modular components that are combined to perform various functions, the performance of the modular components in combination and, thus, the performance of the measurement system as a whole, is often is difficult to predict, making it difficult to calibrate the system. With respect to modular devices/instrumentation, such as modular receivers, it may be necessary, or at least desirable, to quickly and accurately characterize (e.g., calibrate) a system, including characterizing delay after components of the system are exchanged or the interconnection cabling is modified. Unfortunately, for a given system or device, such as a communications receiver, phase response is typically characterized at the factory, using expensive and bulky test equipment. It may, thus, be impractical to calibrate the system or device on a regular basis. For example, it may be difficult or impractical to calibrate modular component systems in the field as configurations are modified, such as when components of the system are exchanged or the interconnection cabling is modified.